Optical lens system for taking image

ABSTRACT

An optical lens system for taking image comprises: a first lens element with positive refractive power, an Abbe Number of the first lens element being V 1 , and it satisfying the relation: 50&lt;V 1 &lt;60; a second lens element with negative refractive power having a concave object-side surface and a convex image-side surface; a third lens element having a convex object-side surface and a concave image-side surface, at least one of the object-side and the image-side surfaces of the third lens element being aspheric; a fourth lens element having at least one aspheric surface; and an aperture stop being located in front of the second lens element.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical lens system for takingimage, and more particularly to an optical lens system for taking imageused in a miniaturized digital camera.

2. Description of the Prior Art

In recent years, with the popularity of the mobile phone camera, theoptical lens system for taking image has become thinner and thinner, andthe electronic imaging sensor of a general digital camera is typically aCCD (Charge Coupled Device) or CMOS (Complementary Metal OxideSemiconductor) sensor. Due to advances in semiconductor manufacturing,the pixel size of sensors has been reduced continuously, andminiaturized optical lens systems for taking image have increasinglyhigher resolution. Therefore, there's increasing demand for imagequality.

A conventional mobile phone camera usually consists of three lenselements: from the object side to the image side: a first lens elementwith positive refractive power, a second lens element with negativerefractive power and a third lens element with positive refractivepower, such as the optical lens system for taking image described inU.S. Pat. No. 7,145,736.

As the pixel size of electronic imaging sensors gradually becomessmaller and smaller, the system requires higher image quality. Theconventional optical lens system comprising three lens elements cannotsatisfy the requirements of higher resolution optical lens systems.

U.S. Pat. No. 7,365,920 discloses a four-piece lens assembly, in whichthe first lens element and the second lens element, which are bothspherical lens elements, are bonded to each other to form a doublet lensfor eliminating chromatic aberration. However, it suffers from thefollowing disadvantages: the freedom of the optical system isinsufficient since there are too many spherical lens elements; and themanufacturing difficulty is increased due to the difficult process ofbonding glass lens elements.

The present invention mitigates and/or obviates the afore-mentioneddisadvantages.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a newoptical lens system comprising four lens elements for taking image toimprove image quality, and effectively reduce the volume of the opticallens system.

According to one aspect of the present invention, an optical lens systemfor taking image in accordance with the present invention comprises:from the object side to the image side: a first lens element withpositive refractive power; a second lens element with negativerefractive power having a concave object-side surface and a conveximage-side surface and being located behind the first lens element; athird lens element having a convex object-side surface and a concaveimage-side surface and being located behind the second lens element, atleast one of the object-side and the image-side surfaces of the thirdlens element being aspheric; a fourth lens element having at least oneaspheric surface and being located behind the third lens element; and anaperture stop being located before the second lens element.

In the present optical lens system for taking image, typically therefractive power of the system is mainly provided by the first lenselement with positive refractive power. The second lens element withnegative refractive power mainly serves to correct the chromaticaberration. The third lens element and the fourth lens element serve ascorrection lenses to balance and correct various aberrations caused bythe optical lens system.

The first lens element provides a strong positive refractive power, andthe aperture stop is located close to the object side, so that the totaltrack length of the optical lens system can be effectively reduced, andthe exit pupil of the optical lens system will be far away from theimage plane. Therefore, the light will be projected onto the sensor witha relatively small incident angle, this is the telecentric feature ofthe image side, and this feature is very important to the photosensitivepower of current solid-state sensors, since they are more sensitive whenthe light is incident at a small angle. This also reduces theprobability of the occurrence of shading. The inflection points formedon the third lens element and the fourth lens element will contribute toa better correction of the incident angle of the off axis light withrespect to the sensor and makes the peripheral image plane more flat.

In addition, in the wide angle optical system, it is especiallynecessary to correct the distortion and the chromatic aberration ofmagnification, and this can be solved by locating the aperture stop atthe balance point of the refractive power of the system.

In the present optical lens system for taking image, if the aperturestop is located in front of the first lens element, the telecentricfeature of the optical lens system becomes obvious, the total tracklength of the optical lens system will become quite shorter. If theaperture stop is located between the first and second lens elements, thefeature of wide field of view will become obvious, and the opticalsystem is less sensitive as well.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the first lens element has aconvex object-side surface and a convex or concave image-side surface.If the image-side surface of the first lens element is convex, theemphasis is focused on correcting the spherical aberration caused by thesystem. If the image-side surface of the first lens element is concave,the emphasis is focused on correcting the astigmatism. The second lenselement has the concave object-side surface and the convex image-sidesurface. The third lens element has the convex object-side surface andthe concave image-side surface. The fourth lens element has a convexobject-side surface and a concave image-side surface. Such anarrangement can effectively improve the image quality.

With the trend of miniaturization of the optical lens system and therequirement of a large field of view, the focal length of the opticallens system is becoming very short. Therefore, the radius of curvatureand the size of the lens elements must be very small, and it isimpossible to make such glass lens elements by the use of conventionalgrinding. Plastic material is introduced to make lens elements byinjection molding, using a relatively low cost to produce high precisionlens elements. The lens elements are provided with aspheric surfaces,allowing more design parameters (than spherical surfaces), so as tobetter correct aberrations and reduce the number of the lens elements.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the refractive index of the firstlens element is N1, the refractive index of the third lens element isN3, and they satisfy the relations:1.52<N1<1.58;1.52<N3<1.58.

If the refractive index of the first lens element N1 and the refractiveindex of the third lens element N3 satisfy the above relation, theplastic optical material with the refractive index within the aboverange will better match the optical lens system.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the focal length of the opticallens system for taking image is f, the focal length of the first lenselement is f1, the focal length of the second lens element is f2, andthey satisfy the relations:0.8<f/f1<1.2;−0.75<f/f2<−0.3.

If the value of f/f1 is smaller than the above lower limit, therefractive power of the first lens element will be weak, the total tracklength of the system will be too long, and it will be difficult tosuppress the incident angle of the light with respect to the sensor; ifthe value of f/f1 is greater than the above upper limit, the high orderaberrations of the system will be too large. If the value of f/f2 issmaller than the above lower limit, the total track length of the systemwill be too long; if the value of f/f2 is greater than the above upperlimit, it will be difficult to correct the chromatic aberration.Further, it will be better if f/f1 and f/f2 satisfy the relations:0.95<f/f1<1.15;−0.5<f/f2<−0.3.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the focal length of the opticallens system for taking image is f, the focal length of the third lenselement is f3, the focal length of the fourth lens element is f4, andthey satisfy the relations:−0.2<f/f3<0.2;−0.2<f/f4<0.2;

The third lens element and the fourth lens element serve as correctionlens elements to balance and correct various aberrations caused by theoptical lens system.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the on-axis distance between thethird lens element and the fourth lens element is T34, the focal lengthof the optical lens system for taking image is f, and they satisfy therelation:T34/f>0.015.

If T34/f satisfies the above relation, it will be favorable to correctthe high order aberrations of the system.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the Abbe number of the first lenselement is V1, the Abbe number of the second lens element is V2, theAbbe number of the third lens element is V3, and they satisfy therelations:50<V1<60;V1−V2>15;V3−V2>15.

If V1, V2, V3 satisfy the above relations, the chromatic aberration ofthe optical lens system can be more favorably corrected, improving theresolution of the optical lens system. Further, it will be better if V2satisfies the relation:V2<26.8.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the radius of curvature of theobject-side surface of the first lens element is R1, the radius ofcurvature of the image-side surface of the first lens element is R2, andthey satisfy the relation:0.2<R1/R2<05;

If the value of R1/R2 is smaller than the above lower limit, it will bedifficult to correct the astigmatism caused by the system. And if thevalue of R1/R2 is greater than the above upper limit, it will bedifficult to correct the spherical aberration caused by the system.Further, it will be better if R1, R2 satisfy the relation:0.3<R1/R2<0.5.

According to another aspect of the present invention, in the presentoptical lens system for taking image, the optical lens system for takingimage may further comprise an electronic imaging sensor for enabling anobject to be photographed to be imaged on it, a total track length ofthe optical lens system for taking image is TTL, a maximum image heightof the optical lens system for taking image is ImgH, and they satisfythe relation:TTL/ImgH<1.9.

The above relation can maintain the objective of miniaturization of theoptical lens system for taking image.

The present invention will become more obvious from the followingdescription when taken in connection with the accompanying drawings,which show, for purpose of illustration only, the preferred embodimentsin accordance with the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an optical lens system for taking image in accordance witha first embodiment of the present invention;

FIG. 2 shows the aberration curve of the first embodiment of the presentinvention;

FIG. 3 shows an optical lens system for taking image in accordance witha second embodiment of the present invention;

FIG. 4 shows the aberration curve of the second embodiment of thepresent invention;

FIG. 5 shows an optical lens system for taking image in accordance witha third embodiment of the present invention; and

FIG. 6 shows the aberration curve of the third embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, which shows an optical lens system for taking imagein accordance with a first embodiment of the present invention, and FIG.2 shows the aberration curve of the first embodiment of the presentinvention. An optical lens system for taking image in accordance withthe first embodiment of the present invention comprises: from the objectside to the image side:

A plastic first lens element 10 with positive refractive power has aconvex object-side surface 11 and a concave image-side surface 12, andthe object-side surface 11 and the image-side surface 12 of the firstlens element 10 are both aspheric.

A plastic second lens element 20 with negative refractive power has aconcave object-side surface 21 and a convex image-side surface 22, theobject-side surface 21 and the image-side surface 22 of the second lenselement 20 are both aspheric.

A plastic third lens element 30 with positive refractive power has aconvex object-side surface 31 and a concave image-side surface 32, theobject-side surface 31 and the image-side surface 32 of the third lenselement 30 are both aspheric, and inflection points are formed on boththe object-side surface 31 and the image-side surface 32 of the thirdlens element 30.

A plastic fourth lens element 40 with negative refractive power has aconvex object-side surface 41 and a concave image-side surface 42, theobject-side surface 41 and the image-side surface 42 of the fourth lenselement 40 are both aspheric, and inflection points are formed on boththe object-side surface 41 and the image-side surface 42 of the fourthlens element 40.

An aperture stop 50 is located between the first lens element 10 and thesecond lens element 20.

An IR cut filter 60 is located behind the fourth lens element 40 and hasno influence on the focal length of the optical lens system.

An image plane 70 is located behind the IR cut filter 60.

The equation for the aspheric surface profiles of the first embodimentis expressed as follows:

${X(Y)} = {{\left( {Y^{2}/R} \right)/\left( {1 + {{sqrt}\left( {1 - {\left( {1 + k} \right)*\left( {Y/R} \right)^{2}}} \right)}} \right)} + {\sum\limits_{i}{({Ai})*\left( Y^{i} \right)}}}$

wherein:

X: the height of a point on the aspheric lens surface at a distance Yfrom the optical axis, relative to the tangential plane of the asphericsurface vertex;

Y: the distance from the point on the curve of the aspheric surface tothe optical axis;

k: the conic coefficient;

Ai: the aspheric surface coefficient of order i.

In the first embodiment of the present optical lens system for takingimage, the focal length of the optical lens system for taking image isf, the focal length of the first lens element is f1, the focal length ofthe second lens element is f2, the focal length of the third lenselement is f3, the focal length of the fourth lens element is f4, andthey satisfy the relations:f=3.30 [mm];f/f1=1.08;f/f2=−0.36;f/f3=0.06;f/f4=−0.02.

In the first embodiment of the present optical lens system for takingimage, the refractive index of the first lens element is N1, and itsatisfies the relation:N1=1.544.

In the first embodiment of the present optical lens system for takingimage, the refractive index of the third lens element is N3, and itsatisfies the relation:N3=1.530.

In the first embodiment of the present optical lens system for takingimage, the Abbe number of the first lens element is V1, the Abbe numberof the second lens element is V2, the Abbe number of the third lenselement is V3, and they satisfy the relations:V1=56.1;V2=23.4;V1−V2=32.7;V3−V2=32.4.

In the first embodiment of the present optical lens system for takingimage, the on-axis distance between the third lens element and thefourth lens element is T34, the focal length of the optical lens systemfor taking image is f, and they satisfy the relation:T34/f=0.10.

In the first embodiment of the present optical lens system for takingimage, the radius of curvature of the object-side surface of the firstlens element is R1, the radius of curvature of the image-side surface ofthe first lens element is R2, and they satisfy the relation:R1/R2=0.21.

In the first embodiment of the present optical lens system for takingimage, the total track length of the optical lens system for takingimage is TTL, the maximum image height of the optical lens system fortaking image is ImgH, and they satisfy the relation:TTL/ImgH=1.72.

The detailed optical data of the first embodiment is shown in table 1,and the aspheric surface data is shown in table 2, wherein the units ofthe radius of curvature, the thickness and the focal length areexpressed in mm, and HFOV is half of the maximal field of view.

TABLE 1 (Embodiment 1) f(focal length) = 3.30 mm, Fno = 2.45, HFOV (halfof field of view = 34.0 deg. Curvature Focal Surface # Radius ThicknessMaterial Index Abbe # length 0 Object Plano Infinity 1 Lens 11.34730(ASP) 0.502 Plastic 1.544 56.1 3.02 2 6.34670(ASP) 0.047 3 Ape.Stop Plano 0.590 4 Lens 2 −1.47293(ASP)  0.316 Plastic 1.632 23.4 −9.1 5−2.13658(ASP)  0.295 6 Lens 3 1.68423(ASP) 0.366 Plastic 1.530 55.851.41 7 1.65909(ASP) 0.324 8 Lens 4 1.14839(ASP) 0.410 Plastic 1.53055.8 −137.87 9 0.99042(ASP) 0.200 10 IR-filter Plano 0.300 Glass 1.51764.1 11 Plano 0.490 12 Image Plano

TABLE 2 Aspheric Coefficients Surface # 1 2 4 5 6 7 8 9 k = −3.65900E+00−6.59319E+01 2.43333E+00 4.19240E+00 −5.09682E+00 −1.31678E+01−2.21724E+00 −3.88017E+00 A4 = 1.74776E−01 −1.47749E−02 −1.47806E−01−2.36922E−01 −1.62471E−01 −5.15453E−03 −5.95111E−01 −3.14734E−01 A6 =−1.50051E−01 −6.79355E−02 5.32921E−01 4.96371E−01 7.58587E−02−4.87077E−02 5.76464E−01 2.39193E−01 A8 = 2.03865E−01 −8.71980E−02−5.34106E−01 −2.66505E−01 −4.22122E−02 2.35423E−02 −3.56771E−01−1.20334E−01 A10 = −2.50631E−01 1.18175E+00 3.89742E−01 6.95530E−03−9.75276E−03 1.20371E−01 3.05639E−02 A12 = 2.24217E−03 −1.98144E−02−3.74267E−03 A14 = −3.07996E−04 1.25127E−03 1.96390E−04

Referring to FIG. 3, which shows an optical lens system for taking imagein accordance with a second embodiment of the present invention, andFIG. 4 shows the aberration curve of the second embodiment of thepresent invention. The second embodiment of the present inventioncomprises: in order from the object side to the image side:

A first plastic lens element 10 with positive refractive power has aconvex object-side surface 11 and a concave image-side surface 12, theobject-side surface 11 and the image-side surface 12 of the first lenselement 10 are both aspheric.

A plastic second lens element 20 with negative refractive power has aconcave object-side surface 21 and a convex image-side surface 22, theobject-side surface 21 and the image-side surface 22 of the second lenselement 20 are both aspheric.

A plastic third lens element 30 with positive refractive power has aconvex object-side surface 31 and a concave image-side surface 32, theobject-side surface 31 and the image-side surface 32 of the third lenselement 30 are both aspheric, and inflection points are formed on boththe object-side surface 31 and the image-side surface 32 of the thirdlens element 30.

A plastic fourth lens element 40 with positive refractive power has aconvex object-side surface 41 and a concave image-side surface 42, theobject-side surface 41 and the image-side surface 42 of the fourth lenselement 40 are both aspheric, and inflection points are formed on boththe object-side surface 41 and the image-side surface 42 of the fourthlens element 40.

An aperture stop 50 is located between the first lens element 10 and thesecond lens element 20.

An IR cut filter 60 is located behind the fourth lens element 40 and hasno influence on the focal length of the optical lens system.

An image plane 70 is located behind the IR cut filter 60.

The equation for the aspheric surface profiles of the second embodimenthas the same form as that of the first embodiment.

In the second embodiment of the present optical lens system for takingimage, the focal length of the optical lens system for taking image isf, the focal length of the first lens element is f1, the focal length ofthe second lens element is f2, the focal length of the third lenselement is f3, the focal length of the fourth lens element is f4, andthey satisfy the relations:f=3.22 [mm];f/f1=1.02;f/f2=−0.40;f/f3=0.13;f/f4=0.08.

In the second embodiment of the present optical lens system for takingimage, the refractive index of the first lens element is N1, and itsatisfies the relation:N1=1.544.

In the second embodiment of the present optical lens system for takingimage, the refractive index of the third lens element is N3, and itsatisfies the relation:N3=1.544.

In the second embodiment of the present optical lens system for takingimage, the Abbe number of the first lens element is V1, the Abbe numberof the second lens element is V2, the Abbe number of the third lenselement is V3, and they satisfy the relations:V1=56.1;V2=23.4;V1−V2=32.7;V3−V2=32.7.

In the second embodiment of the present optical lens system for takingimage, the on-axis distance between the third lens element and thefourth lens element is T34, the focal length of the optical lens systemfor taking image is f, and they satisfy the relation:T34/f=0.08.

In the second embodiment of the present optical lens system for takingimage, the radius of curvature of the object-side surface of the firstlens element is R1, the radius of curvature of the image-side surface ofthe first lens element is R2, and they satisfy the relation:R1/R2=0.32.

In the second embodiment of the present optical lens system for takingimage, the total track length of the optical lens system for takingimage is TTL, the maximum image height of the optical lens system fortaking image is ImgH, and they satisfy the relation:TTL/ImgH=1.73.

The detailed optical data of the second embodiment is shown in table 3,and the aspheric surface data is shown in table 4, wherein the units ofthe radius of curvature, the thickness and the focal length areexpressed in mm, and HFOV is half of the maximal field of view.

TABLE 3 (Embodiment 2) f(focal length) = 3.22 mm, Fno = 2.45, HFOV (halfof field of view) = 34.5 deg. Curvature Focal Surface # Radius ThicknessMaterial Index Abbe # length 0 Object Plano Infinity 1 Lens 11.25649(ASP) 0.545 Plastic 1.544 56.1 3.18 2 3.90030(ASP) 0.114 3 Ape.Stop Plano 0.555 4 Lens 2 −1.48549(ASP)  0.312 Plastic 1.632 23.4 −8.185 −2.25349(ASP)  0.268 6 Lens 3 1.42408(ASP) 0.400 Plastic 1.544 56.125.03 7 1.43293(ASP) 0.258 8 Lens 4 1.36627(ASP) 0.463 Plastic 1.54456.1 38.89 9 1.28616(ASP) 0.124 10 IR-filter Plano 0.300 Glass 1.51764.1 11 Plano 0.529 12 Image Plano

TABLE 4 Aspheric Coefficients Surface # 1 2 4 5 6 7 8 9 k = 1.71633E−011.28170E+00 2.72344E+00 4.79731E+00 −2.80787E−01 −8.96741E−01−5.08919E+00 −4.04130E+00 A4 = −3.84111E−02 −5.15186E−02 −1.43445E−01−3.56273E−01 −3.46225E−01 −2.51384E−01 −3.69495E−01 −3.06285E−01 A6 =1.95153E−01 4.59128E−01 7.37619E−02 4.71090E−01 5.86214E−02 8.55958E−023.12299E−01 2.19303E−01 A8 = −7.11421E−01 −1.99528E+00 1.03776E+00−1.59042E−01 8.94395E−02 −4.65987E−03 −1.63477E−01 −1.03140E−01 A10 =1.36482E+00 4.39271E+00 −4.32757E+00 −2.97974−01 −1.11329E−01−1.49614E−02 4.63038E−02 2.51586E−02 A12 = −1.33157E+00 −5.31988E+009.26894E+00 9.82198E−01 4.90419E−02 5.88582E−03 −6.44879E−03−2.92546E−03 A14 = 4.67451E−01 2.73314E+00 −4.56111E+00 −3.57802E−01−7.80245E−03 −7.58661E−04 3.61347E−04 1.39728E−04

Referring to FIG. 5, which shows an optical lens system for taking imagein accordance with a third embodiment of the present invention, FIG. 6shows the aberration curve of the third embodiment of the presentinvention. The third embodiment of the present invention comprises: inorder from the object side to the image side:

A first plastic lens element 10 with positive refractive power has aconvex object-side surface 11 and a concave image-side surface 12, theobject-side surface 11 and the image-side surface 12 of the first lenselement 10 are both aspheric.

A plastic second lens element 20 with negative refractive power has aconcave object-side surface 21 and a convex image-side surface 22, theobject-side surface 21 and the image-side surface 22 of the second lenselement 20 are both aspheric.

A plastic third lens element 30 with negative refractive power has aconvex object-side surface 31 and a concave image-side surface 32, theobject-side surface 31 and the image-side surface 32 of the third lenselement 30 are both aspheric, and inflection points are formed on boththe object-side surface 31 and the image-side surface 32 of the thirdlens element 30.

A plastic fourth lens element 40 with positive refractive power has aconvex object-side surface 41 and a concave image-side surface 42, theobject-side surface 41 and the image-side surface 42 of the fourth lenselement 40 are both aspheric, and inflection points are formed on boththe object-side surface 41 and the image-side surface 42 of the fourthlens element 40.

An aperture stop 50 is located between the first lens element 10 and thesecond lens element 20.

An IR cut filter 60 is located behind the fourth lens element 40 and hasno influence on the focal length of the optical lens system.

An image plane 70 is located behind the IR cut filter 60.

The equation for the aspheric surface profiles of the third embodimenthas the same form as that of the first embodiment.

In the third embodiment of the present optical lens system for takingimage, the focal length of the optical lens system for taking image isf, the focal length of the first lens element is f1, the focal length ofthe second lens element is f2, the focal length of the third lenselement is f3, the focal length of the fourth lens element is f4, andthey satisfy the relations:f=3.31 [mm];f/f1=1.14;f/f2=−0.40;f/f3=−0.06;f/f4=0.10.

In the third embodiment of the present optical lens system for takingimage, the refractive index of the first lens element is N1, and itsatisfies the relation:N1=1.544.

In the third embodiment of the present optical lens system for takingimage, the refractive index of the third lens element is N3, and itsatisfies the relation:N3=1.544.

In the third embodiment of the present optical lens system for takingimage, the Abbe number of the first lens element is V1, the Abbe numberof the second lens element is V2, the Abbe number of the third lenselement is V3, and they satisfy the relations:V1=56.1;V2=23.4;V1−V2=32.7;V3−V2=32.7.

In the third embodiment of the present optical lens system for takingimage, the on-axis distance between the third lens element and thefourth lens element is T34, the focal length of the optical lens systemfor taking image is f, and they satisfy the relation:T34/f=0.08.

In the third embodiment of the present optical lens system for takingimage, the radius of curvature of the object-side surface of the firstlens element is R1, the radius of curvature of the image-side surface ofthe first lens element is R2, and they satisfy the relation:R1/R2=0.22.

In the third embodiment of the present optical lens system for takingimage, the total track length of the optical lens system for takingimage is TTL, the maximum image height of the optical lens system fortaking image is ImgH, and they satisfy the relation:TTL/ImgH=1.73.

The detailed optical data of the third embodiment is shown in table 5,and the aspheric surface data is shown in table 6, wherein the units ofthe radius of curvature, the thickness and the focal length areexpressed in mm, and HFOV is half of the maximal field of view.

TABLE 5 (Embodiment 3) f(focal length) = 3.31 mm, Fno = 2.45, HFOV (halfof field of view) = 34.0 deg. Curvature Focal Surface # Radius ThicknessMaterial Index Abbe # length 0 Object Plano Infinity 1 Lens 11.29077(ASP) 0.562 Plastic 1.544 56.1 2.9 2 5.98090(ASP) 0.048 3 Ape.Stop Plano 0.507 4 Lens 2 −1.43522(ASP)  0.344 Plastic 1.632 23.4 −8.255 −2.16389(ASP)  0.309 6 Lens 3 1.76201(ASP) 0.372 Plastic 1.544 56.1−57.83 7 1.54444(ASP) 0.271 8 Lens 4 1.25321(ASP) 0.482 Plastic 1.53055.8 31.86 9 1.17334(ASP) 0.200 10 IR-filter Plano 0.300 Glass 1.51764.1 11 Plano 0.474 12 Image Plano

TABLE 6 Aspheric Coefficients Surface # 1 2 4 5 6 7 8 9 k = −3.37450E+00−6.75926E+01 2.71824E+00 4.52769E+00 −4.13081E+00 −1.29561E+01−1.82404E+00 −3.61960E+00- A4 = 1.89816E−01 −1.35367E−02 −1.37477E−01−2.05949E−01 −1.73171E−01 −3.79245E−03 −5.93590E−01 −3.19459E−01 A6 =−1.37891E−01 −7.83622E−02 5.23756E−01 4.44448E−01 7.34159E−02−4.69829E−02 5.75712E−01 2.39775E−01 A8 = 1.71544E−01 −2.13284E−01−7.55989E−01 −2.58272E−01 −3.77955E−02 2.29643E−02 −3.56794E−01−1.19836E−01 A10 = −1.80074E−01 1.47256E−01 1.82420E+00 4.31755E−016.24241E−03 −1.00581E−02 1.20361E−01 3.05028E−02 A12 = −6.60094E−022.45555E−03 −1.98263E−02 −3.73899E−03 A14 = −3.13819E−04 1.25188E−031.90911E−04

TABLE 7 Embodiment 1 Embodiment 2 Embodiment 3 f 3.30 3.22 3.31 Fno 2.452.45 2.45 HFOV 34.0 34.5 34.0 N1 1.544 1.544 1.544 N3 1.530 1.544 1.544V1 56.1 56.1 56.1 V2 23.4 23.4 23.4 V1 − V2 32.7 32.7 32.7 V3 − V2 32.432.7 32.7 f/f1 1.08 1.02 1.14 f/f2 −0.36 −0.40 −0.40 f/f3 0.06 0.13−0.06 f/f4 −0.02 0.08 0.10 T34/f 0.10 0.08 0.08 R1/R2 0.21 0.32 0.22TTL/ImgH 1.72 1.73 1.73

It is to be noted that the tables 1-6 show different data from thedifferent embodiments, however, the data of the different embodiments isobtained from experiments. Therefore, any product of the same structureis deemed to be within the scope of the present invention even if ituses different data. Table 7 lists the relevant data for the variousembodiments of the present invention.

While we have shown and described various embodiments in accordance withthe present invention, it should be clear to those skilled in the artthat further embodiments may be made without departing from the scope ofthe present invention.

1. An optical lens system for taking image comprising, from the objectside to the image side: a first lens element with positive refractivepower, an Abbe number of the first lens element being V1, and itsatisfying the relation: 50<V1<60; a second lens element with negativerefractive power having a concave object-side surface and a conveximage-side surface, the second lens element being located behind thefirst lens element; a third lens element having a convex object-sidesurface and a concave image-side surface, the third lens element beinglocated behind the second lens element, at least one of the object-sideand the image-side surfaces of the third lens element being aspheric; afourth lens element having at least one aspheric surface, the fourthlens element being located behind the third lens element; and anaperture stop being located before the second lens element; wherein: inthe optical lens system for taking image, the number of the lenselements with refractive power is only four; the fourth lens element ismade of plastic material and has a convex object-side surface and aconcave image-side surface, both the object-side surface and theimage-side surface of the fourth lens element are aspheric.
 2. Theoptical lens system for taking image as claimed in claim 1, wherein thefirst lens element is made of plastic material, both an object-sidesurface and an image-side surface of the first lens element areaspheric, the second lens element is made of plastic material, both theobject-side surface and the image-side surface of the second lenselement are aspheric, the third lens element has positive refractivepower and is made of plastic material, both the object-side surface andthe image-side surface of the third lens element are aspheric.
 3. Theoptical lens system for taking image as claimed in claim 2, wherein theobject-side surface of the first lens element is convex, and theimage-side surface of the first lens element is concave.
 4. The opticallens system for taking image as claimed in claim 1, wherein inflectionpoints are formed on both the third lens element and the fourth lenselement.
 5. The optical lens system for taking image as claimed in claim3, wherein a refractive index of the first lens element is N1, arefractive index of the third lens element is N3, and they satisfy therelations:1.52<N1<1.58;1.52<N3<1.58.
 6. The optical lens system for taking image as claimed inclaim 5, wherein the Abbe number of the first lens element is V1, anAbbe number of the second lens element is V2, an Abbe number of thethird lens element is V3, and they satisfy the relations:V1−V2>15;V3−V2>15.
 7. The optical lens system for taking image as claimed inclaim 6, wherein the Abbe number of the second lens element is V2, andit satisfies the relation:V2<26.8.
 8. The optical lens system for taking image as claimed in claim1, wherein an on-axis distance between the third lens element and thefourth lens element is T34, a focal length of the optical lens systemfor taking image is f, and they satisfy the relation:T34/f>0.015.
 9. The optical lens system for taking image as claimed inclaim 1, wherein the focal length of the optical lens system for takingimage is f, a focal length of the third lens element is f3, a focallength of the fourth lens element is f4, and they satisfy the relations:−0.2<f/f3<0.2;−0.2<f/f4<0.2.
 10. The optical lens system for taking image as claimedin claim 1, wherein the focal length of the optical lens system fortaking image is f, a focal length of the first lens element is f1, afocal length of the second lens element is f2, and they satisfy therelations:0.8<f/f1<1.2;−0.75<f/f2<−0.3.
 11. The optical lens system for taking image as claimedin claim 10, wherein the focal length of the optical lens system fortaking image is f, the focal length of the first lens element is f1, thefocal length of the second lens element is f2, and they satisfy therelations:0.95<f/f1<1.15;−0.5<f/f2<−0.3.
 12. The optical lens system for taking image as claimedin claim 3, wherein the aperture stop is located between the first lenselement and the second lens element.
 13. The optical lens system fortaking image as claimed in claim 12 further comprising an electronicimaging sensor for enabling an object to be photographed to be imaged onit, a total track length of the optical lens system for taking image isTTL, a maximum image height of the optical lens system for taking imageis ImgH, and they satisfy the relation:TTL/ImgH<1.9.
 14. The optical lens system for taking image as claimed inclaim 1, wherein a radius of curvature of the object-side surface of thefirst lens element is R1, a radius of curvature of the image-sidesurface of the first lens element is R2, and they satisfy the relation:0.3<R1/R2<0.5.
 15. The optical lens system for taking image as claimedin claim 12, wherein the radius of curvature of the object-side surfaceof the first lens element is R1, the radius of curvature of theimage-side surface of the first lens element is R2, and they satisfy therelation:0.3<R1/R2<0.5.
 16. An optical lens system for taking image comprising,from the object side to the image side: a first lens element withpositive refractive power, an Abbe number of the first lens elementbeing V1, and it satisfying the relation: 50<V1<60; a second lenselement with negative refractive power having a concave object-sidesurface and a convex image-side surface, the second lens element beinglocated behind the first lens element; a third lens element having aconvex object-side surface and a concave image-side surface, the thirdlens element being located behind the second lens element, at least oneof the object-side and the image-side surfaces of the third lens elementbeing aspheric; a fourth lens element having at least one asphericsurface, the fourth lens element being located behind the third lenselement; and an aperture stop being located before the second lenselement; wherein: in the optical lens system for taking image, thenumber of the lens elements with refractive power is only four; and aradius of curvature of the object-side surface of the first lens elementis R1, a radius of curvature of the image-side surface of the first lenselement is R2, and they satisfy the relation:0.3<R1/R2<0.5.
 17. The optical lens system for taking image as claimedin claim 16, wherein the Abbe number of the second lens element is V2,and it satisfies the relation:V2<26.8.
 18. The optical lens system for taking image as claimed inclaim 16 further comprising an electronic imaging sensor for enabling anobject to be photographed to be imaged on it, a total track length ofthe optical lens system for taking image is TTL, a maximum image heightof the optical lens system for taking image is ImgH, and they satisfythe relation:TTL/ImgH<1.9.
 19. The optical lens system for taking image as claimed inclaim 17, wherein the focal length of the optical lens system for takingimage is f, a focal length of the third lens element is f3, a focallength of the fourth lens element is f4, and they satisfy the relations:−0.2<f/f3<0.2;−0.2<f/f4<0.2.
 20. The optical lens system for taking image as claimedin claim 17, wherein the focal length of the optical lens system fortaking image is f, a focal length of the first lens element is f1, afocal length of the second lens element is f2, and they satisfy therelations:0.8<f/f1<1.2;−0.75<f/f2<−0.3.